High-performance motor control chip with multi-core architecture

Advances in many aspects of motor design, motor manufacturing, materials, motor control and sensor technology have promoted the development of modern motors, and the application range of motors is increasingly wide, especially in new applications such as medical equipment, automotive appliances and mobile robots. The progress of motor control technology is the most important factor to promote the development of motor technology in recent years, however, due to the high technical barriers related to motor control, such as the electromagnetic principle of the motor, signal processing, digital chips, analog chips and power semiconductors, the development of motor control chips is facing many technical bottlenecks, especially in the realization of special motor control chips.

Many conventional motors, such as induction motors that do not require speed regulation, can be driven directly by alternating current (AC) without the need for an electronic control system. However, modern electromechanical systems usually need to adjust the operation of the motor, which requires the use of electronic controllers to control the operation of the motor to achieve the desired operating state, such as speed, position, steering, torque and power.

In addition to the need to achieve the desired operating state, modern motor control systems also need to achieve many additional functions, such as the ability to achieve the desired regulation effect with low energy consumption, high efficiency and low noise, the realization of the required communication mode, and the ability to effectively protect the motor system. New requirements are still emerging.

A motor control system requires a variety of active electronics, including main control chips, front drivers, power semiconductors, and sensors. The traditional motor control chip uses a single-core MCU to process the control signal, and realizes the required control mode through the encoded program stored in the chip, and then outputs the control voltage or current according to the requirements of the control mode, and finally realizes the required motor running state.

When the required control power is large (such as 10kW or more), the size and price of the control chip are often not the main factors in determining whether the control system is accepted by the market. However, for applications with less motor power, the situation is different. For example, in the large market of data center server cooling fan applications, a single motor control chip contains the MCU, front driver, and low-power semiconductor, so that the entire control system can be implemented on a simple printed circuit board, as shown in Figure 1. When applications require a few hundred to one kilowatt of power, such as air conditioning ventilation fans, an IPM (Intelligent Power module) containing an MCU, a front driver, and a high-power MOSFETs can be used, as shown in the example in Figure 2. In both applications, the size and cost-effectiveness of the controller often determine the success or failure of the product in the market. In terms of volume, the market for low-power motor controllers is much larger than that for high-power motor controllers. Therefore, the field of small power motors is the main market to promote the development of motor control chips, especially special motor control chips.

Unlike the use of software and general purpose DSP to control motors, special motor control chips are developed specifically for motor control applications. It solidifies the control algorithm in the form of firmware and integrates the required high-speed operational amplifiers, comparators, Ldos, and many other peripherals into the chip. Therefore, systems that use dedicated motor control chips, especially low-power systems, have fewer electronic components, and the PCB board of the control system is more compact and tidy.
At present, robots are undergoing remarkable development. Modern robots typically have more than 40 "degrees of freedom" (DOF), meaning that the "robot" uses many low-power motor and actuator systems [1]. On the other hand, a car currently typically uses more than 40 motors [2], most of which are low-power motors. In both cases, there are high demands on the size and cost-effectiveness of the motor system (including the control chip)!

Many applications have strict requirements for motor size and reliability. If magnetic sensors (such as Hall sensors) are used in the motor to detect the rotor position, the structure of the motor will become complicated, which is not conducive to the reliability and service life of the motor (Figure 3).

"Sensorless control" uses the algorithm of the "observer" in the controller rather than the physical position sensor to calculate the rotor position of the motor, while adjusting the current and voltage in the stator windings of the motor according to the rotor position and the control mode (such as the FOC mode) to control the state of the motor (Figure 4). This control method does not require additional physical Angle sensors, so it can greatly simplify the motor structure and improve its reliability. However, sensorless control requires high performance observers, such as sliding film observers, adaptive observers, or observers based on scalable Kalman filtering algorithms. Using these observers requires a lot of computation and puts a high demand on MCU performance. Advances in motor control technology and semiconductor hardware have led to the increasing use of sensorless control in motor systems. In the application scenario, sensorless control is insensitive to the magnetization error of the magnet, often can obtain better control effect than sensor-based control, and can completely avoid the sensor position error caused by installation, this control mode has become an important development trend of motor control technology. Many high-performance drive modes, such as FOC (field-oriented control), can also be implemented with sensorless control modes.